The present invention relates to a signal transceiver, and more particularly to a signal transceiver having the characteristics of high linearity and low noise figure.
In a wireless communication system comprising a receiver and a transmitter, an external T/R (Transmitter/Receiver) switch is applied for implementing a Time-Division Duplex (TDD) mode since both the receiver and the transmitter share the same antenna. When the wireless communication system is under operation, the external T/R switch is controlled to switch between the receiver and the transmitter for coupling either the receiver or the transmitter to the antenna. According to one conventional wireless communication system, the external T/R switch is installed in series with the receiver instead of the transmitter. When the external T/R switch is turned ON (i.e. shorted) under the receiving mode, the external T/R switch should have the characteristics of low insertion loss, large input range, low distortion, and low die area, etc. When the external T/R switch is turned OFF (i.e. open) under the transmitting mode, the external T/R switch should have the characteristics of large swing signal handling capability, providing low distortion in its OFF state, and not disrupting the normal transmitting operation or function of the transmitter, etc. Due to the circuit complexity of both the receiver and the transmitter, however, it is very difficult to accomplish the above-mentioned characteristics in the external T/R switch without having to drastically reduce the maximum allowable input RF (Radio Frequency) signal to the receiver and/or the maximum transmitted output power. Therefore, providing a switch that meets the above-mentioned requirements to switch between the receiver and the transmitter in the wireless communication system has become an important issue in this field.